Financial institutions such as National stock exchanges and banks demand that their computing and data storage systems suffer no more down time than a few minutes per year. Retail corporations are willing to pay millions of dollars to minimize the amount of time their computing and data storage systems need to be taken offline for maintenance or upgrade activities. It is important that storage system vendors provide high performance and high availability to satisfy these customers. But, when data storage devices need to be replaced, or swapped, or entire arrays replaced—also referred to as device or array “migration”—applications must suffer some downtime while storage links are disconnected from the original storage devices and reconnected to the new storage devices. It is an as yet unattained and very highly sought goal to provide a storage system wherein currently operating, on-line storage devices, and the data thereon, can be replaced with new storage devices in a non-disruptive manner wherein applications can continue to execute uninterrupted during the device replacement and data migration.